Marker



April 24, 1952 E'. R. GILL, JR 3,030,870

MARKER Filed April 9, 1957 2 Sheets-Sheet 1 I .Ju

" "vf" fffaQ-T .y

"Il \1NVENTOR BY ma.. wccs Nk-R ATTORNEY MARKER 2 Sheets-Sheet 2 Filed April 9, 1957 INVENTOR ATTORNEY ttes This invention relates Ito surface markers and more particularly to road markers and compositions suitable for use as safety lane lines on highways. Y

In the past, trafhc lines, incorporating dry films including a binder having a pigment therein, have served to delineate highways into traflic lanes, particularly under daylight conditions. Y

Under night-time conditions the same system has been utilized wherein the headlamps of Vautomobiles have illuminated the center lines to some limited extent. In subsequent years, prior to the instant invention, this system has been improved by the addition of glass spheres or other autocollimating units to the lines which have served to intensify the reflected light under night-time conditions.

Little or no attention has been paid to the conditions which prevail at dawn and twilight, or the conditions which prevail in between the times of normal day-light and nighttime, or theA conditions which prevail during the daytime but with ther presence of atmospheric conditions which cut down the normal amount of day light for the particular time of day. Such iii-between time conditions usually occur when the traffic flow on the highways is heaviest, and statistics reveal that the greatest number of accidents occur during these periods.

It is therefore an object of the instant invention to provide compositions and safety lane lines which have extremely high visibility at dawn, twilight, and during all periods when the normal amount of day light is not present.

It is a further object of the instant invention not only to teach and provide safety lane lines which will have extremely'high visibility at dawn, twilight or during periods' of corresponding light conditions, but a lane line system which, under these conditions, will continue at high efficiency and with uniform high eicieney throughout a long service period.

It is a still further object of the instant invention not only to provide a lane line system which will be optically efficient for a long period of time under abnormal day light or rresponding light conditions, but also to provide a system which will optically serve to delineate lanes on the highway duringnormal day light conditions and normal e night-time conditions.

Other objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

n FIG. 1 is a view in perspective of a roadway normally bearing vehicular trahie having lane lines applied thereto in accordance with the invention;

FIG. 2 is across-sectional view` through a lane line re'ce'ntly applied;

FIG. 3 isV a cross-sectional viewthrough the lane line shown in FIG. 2 after approximately one month of use;

FIG.' 4 is across-sectional View through the lane line shown in FIG. 2 after approximately seven months of use;

FIG.` 5 isan enlarged view as seen through a magnifying glass-of a portion of thelane'line of FIG. 2; and

FIG.V 6 is adiagrammatic view of the spectrum showing the transformation of the light. v

Referring'to FIG. 1, a roadway is shown marked with a 'pairof` curve lane'lines 10 and a-c'enter lane line 12 2 fabricated in accordance with the present invention, AThe curve lane lines in somel Statesrarre yellow, whereas the center lane is white. Some States likewise require red lane lines.

In accordance with the instant invention, fluorescent dyes, in cooperation with other elements ofthe system, are utilized to intensify the light passing from the lane line to the observer by converting radiant energy corresponding to invisible light or near invisible light into visible light at the most' or highest efficiencygrate for which the system is particularly designed as for day light conditions. The system is further provided with other elements and ingredients which normally protect or shield the underneath fluorescent particles from fluorescing but which, when in association with the highway andpduring normal wear occasioned by vehicular traflic and weathering, are removed sonas to make previously protected or dormant fluorescent particles fluorescent.

This willV be more readily understood when it is appreciated that under averageconditions of vehicular traflic and weathering, a lane line, as heretofore used, having a dry film thickness of approximately 15 mils, has allife of approximately 15 months; thus showing a loss due to wear and weathering of approximately one mil per month of use. In accordance with the present invention, the lane line of approximately 15 mils thickness is provided in each mil of its thickness with an optimum number of fluorescent dye particles or molecules which will, at twilight or like conditions, produce the most efiicient total light emission which will be observed by the driver of `a vehicle. At the same time, it should be noted` that the entire l5 mils may include so many fluorescent dye particles that if they were all yactivated at the same time, they would be wholly ineficient for the purpose intended. However, in accordance with the instant invention, when each outer one mil layer is successively exposed for its lifetime, which may be in some cases equal to an average of one month, then the amount of molecules of uorescent dye which is exposed at any one time is the precise quantity which gives the highest efficiency and the most light emisison to the observer while the remaining fluorescent dye particles in the remaining lower mil layers are kept fully protected by the particularly included particles which each serves as a shield for the radiant energy which would otherwise destroy the fluorescent particles in theselower mil layers. The iluorescent particles in these lower 1 mil thick layers are protected by a large number of embedded pigment particles which serve as shields for the radiant energy striking the upper surface of the lane line, preventing penetration into the lane line of this radiant energy beyond approximately 1 mil of its thickness. The

fluorescent particles contained in the lower mil layers,`

are also protected by small glass spheres which serve as radiant energy filters, and the eiciency of lthese' small glass lters increases with the increase of the index of refraction of the glass over 1.5, so that as the index reaches 2.0 or higher these lters become, for practical purposes, eicient as radiant energy shields. v

Thus it will beunderstood that the pigment particles and the small glass spheres serve to fully protect the fluorescent particles in the fourteen l mil thick layers below the active outer layer of 1 mil thickness, and as the active outer layer is continually worn off by vehicular trafhc and weathering conditions during a period of time averaging theV lifetime of the exposed iluorescent particles when subjected to normal sunlight conditions, each succeeding l mil layer becomes exposed'so that the optimum amount of iluorescent particles in the newly'exposed layer becomes active and active to the extent of optimum efficiency. In this manner, it can be seen that the lane line continuously yields the maximum efficiency during 3 the lifetime of the entire line, yet uses a dye having a much shorter life than the life of the line itself.

The composition used in obtaining a lane line in accordance with the instant invention includes a reflecting binder 20 including ingredients such as will be specified later in detail, and a series of autocollimating units such as relatively small glass spheres 414, in more or less embedded relation.

'Ihe lane line in accordance with this invention may be fabricated by applying to the surface to be marked the binder or paint, which application may be made by spraying, brushing, dipping or otherwise coating. The paint may include autocollimating units as an ingredient therein, or the autocollimating units may be dropped in for reflectivity, while the marker is in a wet, semi-wet, or tacky condition. In the latter case, the autocollimating units are distributed over the surface of the lane line, either by hand or with a mechanical dispenser. The paint is then permitted to dry and hold the autocollimating units. Those units which are partially exposed in combination with the reflecting binder will serve to effect the rellection of light back to the source emanating light thereto, and with subsequent wear of the line, successive layers of the paint containing the reflective binder and glass spheres will be exposed, thus maintaining the line at highest elllciency for use twenty-four hours per day.

'Ille paint composition in accordance with this invention includes a pigment 18, a vehicle 2), and a volatile component. The paint composition may comprise approximately 50% volatiles and 50% non-volatiles, the non-volatiles including both the pigment and vehicle to which may be added the glass spheres 14 at the rate of six pounds per gallon of paint. The non-volatile ingredients, other than the pigment, comprising the vehicle, may comprise oils or resins or both, and the fluorescent dye particles 16. The resins may be natural or synthetic.

A suitable highway marking formula suitable for use in the instant invention should have the following characteristics:

(1) The mechanical qualities required to resist abrasion due to traflic and exposure to the elements.

(2) Ability to retain the autocollimating units.

(3) Compatibility of the paint with the fluorescent dye particles.

(4) A reasonably good dielectric constant.

(5) Non-conductivity.

Although the lrst three characteristics listed above are self-explanatory, the latter two will require some explanation. In the present invention, a fluorescent dye material is incorporated in the paint composition, which material is responsive to the energy in the incident light to transform the radiant energy corresponding to invisible light or near invisible light into visible light, thereby increasing the light normally rellected many fold by the combination of the reflected light and the fluorescence resulting from this transformation of the radiant energy into light.

When a quantum of energy or a photon falls on a molecule or atom of an aromatic compound capable of fluorescence and is absorbed, the energy level of the molecule is thereby raised. In order to return to its normal condition, the molecule must release this acquired energy. It can do so in several ways, such as heat, electrical energy, chemical change or as radiation in the form of visible light. The latter is the objective of the instant invention and for maximum eciency, the others must be suppressed as much as possible. Dissipation of this energy in the other forms will not occur excessively if conditions favor the release of the lacquired energy as light rays. By providing for facile radiation, and using a stable dyestuff, the photo-chemical action is minimized. If the media in which the fluorescent molecules are contained has conductance, the absorbed energy may be released internally electrically. This can be prevented by maintaining the media non-conductive. Thus, aluminum or other metal flakes, and easily ionized salts as potential electrolytes must be avoided. Actual tests have indicated that the presence of metal ilakes in any proportion was injurious, and an amount barely visible in the formula, killed all trace of fluorescence.

A high dielectric constant in the media surrounding the molecules of dyestuff is desirable so that the molecules will be isolated from one another. The addition to the vehicle of certain additives serves to increase the dielectric constant thereof. In general, the dielectric constant should be greater than that of air and generally not less than 2.5. As best shown in the enlarged FIG. 5, each particle of dye 16 is surrounded by a lllm of the vehicle 20. The dye particles are separated from each other by a distance of at least the mean dimension of the dye molecule, with the lm of vehicle acting as an insulator between particles.

The volatile portion of the paint composition may be composed of one of several solvents adjusted to the drying and set-up rate desired. Such solvents as mineral spirits, alcohols, benzol, xylol, toluol, naphtha, gasoline, turpentine and the like, are suitable.

The pigments 18 suitable for use as ingredients in these compositions are conventional pigments excluding those that comprise metallic salts which ionize readily such as zinc salts, iron oxides, calcium sulfate, barium sulfate and the like. Preferred pigments are the titanium derivatives such as titanium dioxide and barium titanate. These materials give an excellent white, the diffuse reflection is high, and they are not subject to change. Other materials that can be used as extenders include magnesium silicate, various carbonates, diatomaceous silica, amorphous and crystalline silica, micaceous materials and the like which are inert chemically and electrically.

As the vehicle 20, a number of materials may be included such as natural resins and some of their glycerol esters, including rosin, rosin ester, Congo, Congo ester, Manila, Manila ester, dammar, sandarac, mastic, pontianac, East India, kauri and shellac. Synthetic resins may also be used such as glycerol phthalate, ethylene glycol phthalate, pentaerythritol phthalate, vinyl acetate polymers, phenol-formaldehyde condensation products, modified phenol-formaldehyde, formaldehyde resins, para coumarone-indene (cumar) resin, chlorinated diphenyl resin, and cyclo hexanone formaldehyde resin. Drying and semi-drying oils may also be incorporated such as tung oil, China-wood oil, rellned linseed oil, linseed oil (kettle bodied), oiticica oil, poppy seed oil, castor oil, soya bean oil, sunflower oil and glycerol.

Also to be included in the vehicle is up to 1% thereof of a lluorescent dye. A good lluorescent dye includes those possessing relatively pale, but bright, tinctorial power, such as red, orange, yellow, blue or violet, which are attended with macroluminescence in the visible color so outstanding as to be easily recognized. The fluorescent dyes suitable should have the following properties or characteristics:

(l) Bright color-dyestufs are unsuitable where the tincture is black, brown or deep green. Deeper shades of reds, violets and blues are likewise unsuitable.

(2) Responsive to, and absorbent of incident radiation in broad bands throughout the near ultraviolet and even in the shorter visible wave lengths.

(3) The reilection and reradiation substantially coincident on a relatively narrow continuous band of visible wave lengths, so as to increase the brilliance or intensity thereof.

(4) Ellicient quantum conversion, approaching unity.

(5 Photo-chemically insensitive.

(6) Reasonable stability.

(7) Compatibility with the resins, pigments, oils, and volatile solvents used in the highway marking paint.

(8) The luminescent compound should iluoresce substantially the same wave length it reflects.

The derivatives of Quinoline, Acridine, Xanthene, Phthalein, Primulin and Thioflavin, among others, show a bright fluorescence, and many of the derivatives Vin `these classes have a reflective color which parallels the fluorescent emission. Suitable fluorescent dyes meeting the requirements of this invention will be found in The Handbook of Fluorescent Chemicals, Vol. III, Dictionary of Luminescent Substances, Chemical Publishing Co., 1945; Colour Index (F. M. Rowe, editor) 1928; and The Luminescent Dyestuff Index (J. De Ment), 1945. The latter volume contains data on the fluorescence of dyes, their chemical nature, physical properties, chemical structure, uses, and the literature dealing with the luminescence of a given dyestutf. From these texts, suitable lluorescent dyes for use in accordance with the instant invention can be readily chosen. A suitable dyestuff will augment the luminous intensity and thus produce an illumination several times as intense` as white using natural daylight as the incident source of energy.

The following dyes, and/or their homologs, among many others, might be cited as satisfactory for use in the instant invention:

Rhodamin B (C I. 749) Rhodamin G (Cl. 750) Auramin (C.I. 655) Auramin G (C I. 656) Disullne Green B (C.I. 667) Chlorazol Yellow GX (Cl. 620) Tartrazin G (C.I. 640) The CI. refers to the Colour Index number.

The following few examples have been selected as illustrative of many that could be used.

(1) Example of the Stz'lbelte Dyestus Chlorazol Yellow GX: C1620 Ozoxyazodistilbenetetra sulfonate-Sodium salt C2H16N4O1sS4Na4 Re-Yellowz Fl.-Brilliant Yellow (2) Example of the Ketonimine Dyestujfs A typical road marking composition is as follows:

Parts by Vol. D Solvent-volatile 45 Non-volatile vehicle and pigment 55 The non-volatile vehicle and pigmentmay be an alkyd or other resin, or a mixture of several, with or without an adjusted oil length and other additives, one or more white pigments, preferably titanium dioxide or titanates with or without suitable inert extenders in a pigment volume ratio of about 45%. Up to 1% of the vehicle Weight is the fluorescent dye. Preferably a few parts per thousand by weight of the vehicle have given good results when using Rhodamin B, for example.

The luminescent optical system is composed of the pigment 18, reflex reflecting elements 14 (glass spheres) and the fluorescent dye 16. These three components are distributed throughout the thickness of the lane line, as best shown in FIG. 5, which usually has a dry thickness of approximately 15 mils. In bright daylight, the pigment acts to reflect the daylight as in ordinary highway paints. At night, the glass spheres and pigment coact to reflect the light from the vehicle headilghts back to the driver. During periods of abnormal daylight, such as at dawn and twilight, molecules of dye in the exposed surface are activated by the light and caused to fluoresce thereby transmitting a brilliant light dcline'ating the lane line. The life of these fluorescent dye particles in light is somewhat limited; however, only those particles in the upper surface are exposed to the light at one time due to the shielding and filtering action of the pigment and glass spheres which prevent the light from penetrating more than a few mils at most into the composition. The life of the fluorescent dye particles is preferably approximately equivalent to the life of the upper mil layer of the lane line, so that it is worn away before its useful life has expired, and a new layer of fresh dye particles is exposed to the light. Thus, the life of the lane line may be many fold the life of the fluorescent dye particles, and further, always the most efllcient proportion of particles only are exposed at one time.

In adding the fluorescent dyestulf to the paint, it may be dissolved first in the solvent and then incorporated into the non-volatile ingredients.

The autocollimating units are preferably glass spheres in the order of .001 to 0.25 inch in diameter and six pounds more or less are mixed into each total gallon. The glass spheres may, however, be dropped into the stripe by dispensing machinery while the stripe is still in a tacky condition.

A typical formulation in accordance with this invention is as follows:

Percent by volume Pigment 45 Vehicle 55 The pigment consisted of 50% titanium oxide white and 50% titanium calcium pigment.

The vehicle consisted of a synthetic alkyd resin to which was added three parts per thousand of the vehicle by weight of a fluorescent dyestuff, and five to twentyflve parts per hundred of vehicle of castor oil and/or glycerol.

The dyestu selected may be varied depending upon the color of lane line desired. IFor a nearly white line, small concentrations of any suitable dyestuff may be utilized with a white pigment, and a pale coloration will be noted depending upon the reflected color of the dye. The use of a blue fluorescent dye will enhance the whiteness of the line where a pure white appearing line is desirable.

When a yellow lane line is desired, the concentration of a yellow dye such as auramin or chlorazol yellow GX is increased to nearly onepercent by weight of the vehicle present in the paint, and the line will appear yellow during daylight and night reilection as well as fluorescing yellow at dawn and twilight. When a red marker is desired, the concentration of a red dye such as Rhodamin B is increased to nearly one percent by weight of the vehicle present in the paint, and the marker will appear red. Thisis due to the fact that while there is an optimum concentration of dye that will promote the most active intensity of luminescenctgthe curve of fluorescence is more or less flat over a considerable range. Thus, while the percentage of the luminescent component to the non-volatile vehicle will never exceed 1%, it can be varied according to the desired results and materials used.

The amount of pigment required in the formulation should be between 43-50% by volume of the non-volatile ingredients to insure a matte nish to the dried line and yet yield a durable line. A glossy surface should be avoided since it yields internal reflection.

The present invention is also useful at night on roads lighted by mercury vapor lamps or the equivalent, since the fluorescent material in the line will transform the rays emitted by a mercury vapor lamp into other rays, so that the mixture of rays emitted by this material with the untransformed rays directly emitted by the lamp will supplement the normal spectrum.

Referring to FIG. 6, x-y represents diagrammatically the electromagnetic spectrum between the lowest visible red, 7500 A.U., and the upper limit of ultra violet in 7 natural light, 3000 A.U. The limits of the visible wave lengths are 7500 A.U. and 3950 A.U. which last is in the upper end of the visible violet. This drawing also shows the calories of energy absorbed by excitation with ultra violet light corresponding to the wave length at each conventional color boundary. This information is taken from de Ments book entitled Fluorochemistry, page 35, Table 7, published by Chemical Publishing Company in 1945. The dotted lines and outlined arrows illustrate diagrammatically the theory of the fluorescent component. The smaller arrow 22 represents the normal diffuse reflection of the dyestuif, and the arrow 24 the fluorescent radiation closely coincident. The dotted lines represent the process of light transformation from the spectral bands absorbed to the band in which the radiation takes place. Absorption proceeds in regions of high energy and the iluorescence in a region of lower energy. Moreover, absorption is shown taking place throughout a broad band of frequencies, a width of some 1500-1600 A.U., while the tluorescence is contracted into a narrow band only 150 A.U. in width. At any quantum yield, approaching unity, the intensification resulting in the band between 5900 A.U. and 5750 A.U. will be very great.

It will thus be seen that the tiny dye particles each has a mean dimension in the order of 4 105 mils, which are separated one from another by a non-conducting film which has a dielectric constant greater than air and preferably greater than 2.5. These tiny dye particles embedded beneath the upper surface of the line are shielded from light striking the upper surface of the line by the relatively large glass spheres and pigment particles which are present in a much larger volume as compared to the tiny dye particles. As these glass spheres and pigment particles on the upper surface are worn away along with the exposed vehicle and dye particles, the embedded dye particles, glass spheres and pigment particles become the new top surface. Thus, the lane lines may be considered to be self-rejuvenating during their entire life.

It will be obvious to those skilled in the art that various changes may be made Without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

1. A combined highway `and surface marker comprising a road adapted to receive automotive traffic the upper surface of which is coated with a reileeting pigmented composition having a thickness of approximately 15 mils, said composition including a binder, abou-t 43 to 50% by volume of a nonconductive reflecting pigment, approximately six pounds per gallon of composition of small glass spheres having diameters in the order of 1 to 25 mils distributed throughout the thickness of the marker,

a plurality of fluorescent organic dye particles capable of fluorescing in the presence of light distributed throughout the thickness of the marker yand separated from one another by said binder, pigment particles and glass spheres, said binder being non-conducting and having a dielectric constant of at least 2.5 whereby invisible and near invisible light striking the uper layer of dye particles in said marker are transformed into and reflected as visible light whereas the buried dye particles are shielded by said pigment particles and glass spheres from said light.

2. A highway lane line adapted to receive automotive trailic comprising a reflecting composition having a thickness of approximately 15 mils, said composition including a binder, about 43 to 50% by volume of a non-conductive reflecting pigment, approximately six pounds per gallon of composition of small glass spheres having diameters in the order of 1 to 25 mils distributed throughout the ythickness of the line, a plurality of fluorescent organic dye particles capable of fluorescing in the presence of light distributed throughout the thickness of the line and separated from one another by said hinder, pigment particles and glass spheres, said binder being nonconducting and having a dielectric constant of at least 2.5, whereby Vinvisible and near visible light striking the upper layer of dye particles in said line are transformed into and reflected as visible light whereas the buried dye particles are shielded by said pigment particles and glass spheres from said light.

3. In a highway lane line in accordance with claim 2, wherein the amount of dye particles is in the proportion of from several parts per thousand parts of binder to one part per hundred parts of binder.

4. A combined `highway and surface marker in accordance with claim l, wherein the amount of dye particles is in the proportion of from several parts per thousand parts of binder to one part per hundred parts of binder.

References Cited in the tile of this patent UNITED STATES PATENTS 2,169,657 Millson Aug. 15, 1939 2,330,843 Rodli Oct. 5, 1943 2,379,741 Palmquist July 3, 1945 2,441,559 Burrell May 18, 1948 2,458,104 Schweizer Ian. 4, 1949 2,498,592 Switzer Feb. 21, 1950 2,574,971 Heltzer Nov. 13, 1951 2,574,972 Hill Nov. 13, 1951 2,681,317 Grossman June 15, 1954 2,824,502 Rockwell Feb. 25, 1958 2,837,520 Fusco June 3, 1958 2,895,917 Gaunt July 2l, 1959 2,952,192 Nagin Sept. 13, 1960 YFOREIGN PATENTS 688,310 Great Britain Mar. 4, 1953 

1. A COMBINED HIGHWAY AND SURFACE MARKER COMPRISING A ROAD ADAPTED TO RECEIVE AUTOMOTIVE TRAFFIC THE UPPER SURFACE OF WHICH IS COATED WITH A REFLECTING PIGMENTED COMPOSITION HAVING A THICKNESS OF APPROXIMATELY 15 MILS, SAID COMPOSITION INCLUDING A BINDER, ABOUT 43 TO 50% BY VOLUME OF A NONCONDUCTIVE REFLECTING PIGMENT, APPROXIMATELY SIX POUNDS PER GALLON OF COMPOSITION OF SMALL GLASS SPHERES HAVING DIAMETERS IN THE ORDER OF 1 TO 25 MILS DISTRIBUTED THROUGHOUT THE THICKNESS OF THE MARKER, A PLURALITY OF FLUORESCENT ORGANIC DYE PARTICLES CAPABLE OF FLUORESCING IN THE PRESENCE OF LIGHT DISTRIBUTED THROUGH- 